1. Field of the Invention
The present invention relates to a method of and an apparatus for etching, into a tapered shape, corner edges of lands of an oxide film on a wafer surface in the process of semiconductor device fabrication.
2. Description of the Prior Art
For the fabrication of semiconductor devices such as LSI chips, as shown in FIG. 6 of the accompanying drawings, conductors 101 are formed on a semiconductor substrate 100 by photolithography and dry etching, and then an oxide film 102 of SiO.sub.2 or the like is deposited on the substrate 100 and the conductors 101 by chemical vapor deposition (CVD). Thereafter, a thin insulating or metal film 103 is deposited on the oxide film 102 by CVD.
Semiconductor devices are fabricated through deposition and removal of metal films, oxide films, and other layers. If a lower layer has surface irregularities when an upper layer is to be deposited on the lower layer, i.e., if the conductors 101 have sharp corner edges and the oxide film 102 has lands 102a and recesses 102b, then the lands 102a over the conductors 101 are rounded, and the thin film 103 deposited on the oxide film 102 tends to become irregular in thickness, i.e., become round and thicker around the corner edges of the conductors 101. When another upper layer is deposited on the thin film 103, the thickness of the additional upper layer is liable to be irregular, or as shown in FIG. 6a, the upper layer, denoted at 103a, may not enter the recesses of the oxide film 103, forming voids V. Depending on the conditions in which the thin film 103 is deposited on the oxide film 102, as shown in FIG, 6b, the thin film 103 may possibly form large round convexities over the lands of the oxide film 102, and adjacent large round convexities may laterally contact each other, leaving a void V therebelow.